Remove cluster-enabled from parameters

Continuing my whack-a-mole process of trying to get a Terraform plan
that will apply from
#1443.

It turns out we don't want to set cluster enabled to yes and the default
option is no, so we shouldn't have been trying to change it.

I've been through and compared all the other parameters and they seem to
match.

terraform/deployments/chat/redis.tf

@@ -21,11 +21,6 @@ resource "aws_elasticache_parameter_group" "chat_redis_cluster" {
   name   = local.chat_redis_name
   family = "redis7"
 
-  parameter {
-    name  = "cluster-enabled"
-    value = "yes"
-  }
-
   parameter {
     name  = "maxmemory-policy"
     value = "noeviction"